CN107003456B

CN107003456B - Optical member and image display device having the same

Info

Publication number: CN107003456B
Application number: CN201580066480.4A
Authority: CN
Inventors: 加藤峻也
Original assignee: Fujifilm Corp
Current assignee: Fujifilm Corp
Priority date: 2014-12-11
Filing date: 2015-12-10
Publication date: 2020-08-18
Anticipated expiration: 2035-12-10
Also published as: CN107003456A; US20170276987A1; JP6410840B2; WO2016093290A1; JPWO2016093290A1

Abstract

According to the present invention, there is provided an optical component comprising a substrate and a dot in contact with a surface of the substrate, wherein the dot comprises a liquid crystal material having a cholesteric structure, the substrate comprises a liquid crystal layer on a surface in contact with the dot, and the liquid crystal layer is a layer in which an orientation of a liquid crystal compound is fixed. The optical member of the present invention contains dots containing a liquid crystal material having a cholesteric structure with little alignment disorder in a shape having a large maximum height with respect to the dot diameter, and the detection sensitivity of the dot pattern is high in any direction including the oblique direction. The optical member of the present invention can provide an image display device having excellent sensitivity for data input.

Description

Optical member and image display device having the same

Technical Field

The present invention relates to an optical member and an image display device having the same.

Background

In recent years, there has been an increasing need for a system for inputting data by handwriting with an electronic pen or the like on a display of an image display device. Patent document 1 discloses a transparent sheet having a dot pattern printed on a transparent substrate, the dot pattern including a transparent ink containing a liquid crystal material having a cholesteric structure that selectively reflects infrared rays. The transparent sheet is mounted on a display device, and can be used in the system in combination with an electronic pen having an infrared sensor for detecting reflected light from the dot pattern and an infrared irradiation unit.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 2009-28953

Disclosure of Invention

Technical problem to be solved by the invention

A liquid crystal material having a cholesteric structure has wavelength-selective reflectivity which is the largest in the direction of the cholesteric helical axis, and when it is formed in a planar shape, for example, it has a characteristic of exhibiting the largest reflectivity at a desired wavelength in the direction of the normal line thereof. Therefore, when reading from an oblique direction using the electronic pen or the like in the system as described above, strong reflection cannot be obtained, and it is difficult to obtain high sensitivity. In the transparent sheet of patent document 1, a lyophobic layer is used as a base layer for forming dots, and the surface is largely curved by making a protrusion substantially hemispherical. With this shape, reading with high sensitivity can be performed even in an oblique direction.

On the other hand, in order to form a cholesteric structure of a liquid crystal material having high selective reflectivity, it is preferable that the alignment of the liquid crystal compound is less disturbed. Therefore, a layer having a cholesteric structure is formed on the surface of the alignment film or the like. The lyophobic layer described in patent document 1 is formed from a composition containing a crosslinkable monomer, but does not function as an alignment film. Therefore, it is considered that sufficient selective reflectivity according to the material used for the dots is not obtained in the transparent sheet of patent document 1.

The invention provides an optical component having a dot pattern including a liquid crystal material having a cholesteric structure, wherein the dot pattern has high detection sensitivity in any direction including an oblique direction. Specifically disclosed is an optical component which contains dots made of a liquid crystal material having a cholesteric structure and a small alignment disorder in a shape having a large maximum height relative to the dot diameter. Another object of the present invention is to provide an image display device capable of inputting data, which has excellent sensitivity of data input.

Means for solving the technical problem

As a result of intensive studies to solve the above problems, the present inventors have found that a layer formed by aligning a liquid crystal compound is used as a base layer for forming dots, whereby the liquid crystal material can be well aligned and dots having a large maximum height with respect to the dot diameter can be formed, and have completed the present invention.

Namely, the present invention provides the following [1] to [16 ].

[1] An optical member is provided, which comprises a base,

which has a substrate and a point contacting with the surface of the substrate,

the dots comprise a liquid crystal material having a cholesteric structure,

the substrate includes a liquid crystal layer at a contact surface with the dot,

the liquid crystal layer is a layer in which the orientation of the liquid crystal compound is fixed.

[2] The optical member according to [1], wherein the liquid crystal layer is a layer in which a horizontal orientation of a rod-like liquid crystal compound is fixed.

[3] The optical member according to [2], wherein the liquid crystal layer is a cured layer of a composition containing a polymerizable rod-like liquid crystal compound.

[4] The optical member according to any one of [1] to [3], wherein the liquid crystal layer contains a surfactant.

[5] The optical member according to any one of [1] to [4], wherein the substrate includes an alignment film, and the liquid crystal layer is in direct contact with the alignment film.

[6] The optical member according to any one of [1] to [5], wherein the substrate includes a support.

[7] The optical member according to any one of [1] to [6], wherein the liquid crystal material is obtained by curing a liquid crystal composition containing a liquid crystal compound and a chiral agent.

[8] The optical member according to [7], wherein the liquid crystal composition contains a surfactant.

[9] The optical member according to [8], wherein the surfactant is a fluorine-based surfactant.

[10] The optical member according to any one of [1] to [9], wherein the surface of the substrate has a plurality of dots in a pattern.

[11] The optical member according to any one of [1] to [10], wherein the dots have a diameter of 20 to 200 μm.

[12] The optical member according to any one of [1] to [11], wherein a value obtained by dividing a maximum height of the dot by a diameter of the dot is 0.13 to 0.30.

[13] The optical member according to any one of [1] to [12], wherein the dots have wavelength selective reflectivity having a center wavelength in an infrared light region.

[14] The optical member according to [13], wherein the dots have wavelength selective reflectivity having a center wavelength within a wavelength range of 800 to 950 nm.

[15] The optical member according to any one of [1] to [14], which is transparent.

[16] An image display device having the optical member of [15 ].

Effects of the invention

According to the present invention, a novel optical member can be provided. The optical member of the present invention can be used as an optical member for inputting data by directly handwriting with an electronic pen or the like on an image display device by being attached to a display of the image display device, for example. By using the optical member of the present invention, it is possible to input data with high sensitivity even when an operation with an electronic pen or the like is performed from an oblique direction.

Drawings

Fig. 1 is a schematic cross-sectional view showing an example (1) not including an overcoat layer and an example (2) including an overcoat layer as examples of the optical member of the present invention.

Fig. 2 is a schematic diagram of a system in which the optical member of the present invention is used as a sheet attached to the front surface or the front side of an image display device (display device capable of displaying an image).

Fig. 3 is a retroreflective image showing the optical member of example 1 having a polar angle of 5 degrees. The center of each dot shows a green reflection.

Fig. 4 is a view showing an image obtained by observing a cross section of a spot of the optical member produced in example using a Scanning Electron Microscope (SEM).

Detailed Description

The present invention will be described in detail below.

In the present specification, "to" is used to mean that numerical values described before and after the "to" are included as a lower limit value and an upper limit value.

In the present specification, unless otherwise specified, an angle such as "45 degrees", "parallel", "perpendicular", or "orthogonal" means that the difference from a strict angle is within a range of less than 5 degrees. The difference from the strict angle is preferably less than 4 degrees, more preferably less than 3 degrees.

In the present specification, "(meth) acrylate" is used in the meaning of "either or both of acrylate and methacrylate".

In the present specification, the numerical values, numerical ranges, and qualitative expressions (for example, expressions such as "the same") are to be interpreted as indicating the numerical values, numerical ranges, and properties including errors generally allowable in the technical field. In particular, in the present specification, the terms "whole", "average", or "entire surface" and the like include not only 100% but also an error range which is generally allowable in the technical field, and for example, 99% or more, 95% or more, or 90% or more.

The visible light is light of a wavelength that can be observed by the human eye among electromagnetic waves, and represents light in a wavelength range of 380nm to 780 nm. The invisible light is light in a wavelength region of less than 380nm or in a wavelength region of more than 780 nm.

Of infrared light, near-infrared light is electromagnetic waves having a wavelength range of 780nm to 2500 nm. The ultraviolet light has a wavelength of 10 to 380 nm.

In the present specification, the retroreflection means reflection of incident light in an incident direction.

In the present specification, "polar angle" means an angle with respect to a normal line of a substrate.

In the present specification, the term "surface of a dot" means a surface or an interface of a dot on the opposite side of a substrate, and means a surface not in contact with the substrate. In addition, the surface of the dot is not prevented from contacting the substrate at the end of the dot.

In the present specification, when it is referred to as transparent,

specifically, the light transmittance may be 50% or more, may be 70% or more, and is preferably 85% or more. The light transmittance is a visible light transmittance determined by the method described in JIS a 5759. That is, the transmittance of 380nm to 780nm was measured using a spectrophotometer, and the visible light transmittance was obtained by multiplying the transmittance by a weight coefficient obtained from the spectral distribution of CIE (commission internationale de l' eclairage) sunlight D65, the wavelength distribution of CIE brightness adaptation standard specific visibility, and the wavelength interval, and then performing weighted averaging.

In the present specification, "haze" represents a value measured using a haze meter NDH-2000 manufactured by Nippon Denshoku Industries Co.Ltd.

Theoretically, the haze represents a value represented by the following formula.

(scattering transmittance of natural light of 380 to 780 nm)/(scattering transmittance of natural light of 380 to 780nm + parallel light transmittance of natural light) × 100%

The scattering transmittance is a value calculated by subtracting the parallel light transmittance from the obtained omnidirectional transmittance using a spectrophotometer and an integrating sphere unit. The parallel light transmittance is a transmittance at 0 degrees based on a value measured by using an integrating sphere unit.

< optical component >

The optical member includes a substrate and dots formed on the substrate.

The shape of the optical member is not particularly limited, and may be, for example, a film, a sheet, or a plate. Fig. 1 schematically shows a cross-sectional view of an example of an optical member according to the present invention. In the example shown in fig. 1(1), dots 1 are formed on the surface of the substrate 2 on the liquid crystal side, which includes the support 3 and the liquid crystal layer 4. In the example shown in fig. 1(2), an overcoat layer 5 is further provided on the dot formation surface side of the substrate so as to cover the dots 1.

The optical member of the present invention may or may not be transparent in the visible light region depending on the application, but is preferably transparent.

The haze of the optical member of the present invention is preferably 5% or less, more preferably 3% or less, and particularly preferably 2% or less.

< substrate >

The substrate included in the optical member of the present invention functions as a base material for forming dots on the surface.

The substrate preferably has a low reflectance of light in a wavelength at which light is reflected by dots, and preferably does not contain a material that reflects light in a wavelength at which light is reflected by dots.

The substrate is preferably transparent in the visible light region. Also, the substrate may be colored, but is preferably uncolored or lightly colored. The refractive index of the substrate is preferably about 1.2 to 2.0, more preferably about 1.4 to 1.8. For example, in an optical member used in a front surface of a display, the visibility of an image displayed on the display is not reduced.

Each layer included in the substrate preferably has a low light reflectance at a wavelength at which light is reflected at points, and preferably does not include a material that reflects light at a wavelength at which light is reflected at points. Further, each layer included in the substrate is preferably transparent. The refractive index of each layer is preferably about 1.2 to 2.0, more preferably about 1.4 to 1.8.

The thickness of the substrate is not particularly limited and may be selected according to the application, but is about 5 to 1000. mu.m, preferably 10 to 250. mu.m, and more preferably 15 to 150. mu.m.

The substrate includes a liquid crystal layer. The substrate may include only the liquid crystal layer, but preferably includes a support and the liquid crystal layer, or includes a support, an alignment layer, and the liquid crystal layer.

< liquid Crystal layer >

The liquid crystal layer is a layer included in the substrate and is located on the outermost surface of the substrate. The surface of the substrate where the liquid crystal layer is located is formed with dots. That is, the liquid crystal layer is disposed in contact with the point.

The liquid crystal layer is a layer in which the orientation of the liquid crystal compound is fixed. The present inventors have found that the liquid crystal layer serves as a base layer exhibiting liquid repellency necessary for forming dot shapes and also functions as an alignment layer for forming cholesteric structures. Conventionally, cholesteric alignment is formed by coating a cholesteric structure-forming composition on the surface of an alignment film or a rubbed substrate, but the surface of the alignment film or the rubbed substrate cannot have a liquid repellency necessary for forming a dot shape. In the following examples, it is shown that dots exhibiting high retroreflectivity can be obtained by using a liquid crystal layer even for light incident on the dots at a polar angle of 5 degrees or light incident on the dots at 30 degrees. This indicates that the liquid crystal layer has good liquid repellency and alignment properties as a base layer for forming dots, and dots including a liquid crystal material having a cholesteric structure with little alignment disorder can be formed in a shape having a large maximum height with respect to the dot diameter.

The liquid crystal layer is an aligned layer of a liquid crystal compound, and generally has a front retardation. The front phase difference of a predetermined wavelength can be measured by causing light of the above wavelength to be incident in a film normal direction in KOBRA 21ADH or WR (Oji Scientific Instruments co., ltd). The retardation of the liquid crystal layer in the front is not particularly limited, and may be, for example, 0.1 to 1000nm, 1 to 500nm, or 5 to 300 nm. The front phase difference may be adjusted in accordance with the use of the optical member or in accordance with the image display device used in combination.

The thickness of the liquid crystal layer is not particularly limited, but is preferably 0.01 to 5 μm, and more preferably 0.05 to 3 μm.

[ method of Forming liquid Crystal layer ]

The liquid crystal layer can be formed by, for example, applying a liquid crystal composition described later to the surface of a support, an alignment layer, or the like, drying the composition, and curing the composition as needed. The liquid crystal layer may be formed on a dummy support and then the dummy support may be peeled off.

The coating method is not particularly limited and can be appropriately selected according to the purpose, and examples thereof include a wire bar coating method, a curtain coating method, an extrusion coating method, a direct gravure coating method, a reverse gravure coating method, a die coating method, a spin coating method, a dip coating method, a spray coating method, a slide coating method, and the like.

(drying of liquid Crystal composition)

The liquid crystal composition used on the surface of the substrate may be dried as necessary. The liquid crystal compound in the liquid crystal composition may be aligned in the drying or heating step for drying or heating after drying. The liquid crystal compound in the liquid crystal composition is preferably aligned horizontally with respect to the substrate surface. Further, the liquid crystal layer is preferably a layer in which the horizontal alignment of the liquid crystal compound is fixed. A nematic phase may be formed by horizontal alignment. In this case, the liquid crystal compound is preferably a rod-like liquid crystal compound. The nematic phase is a state in which liquid crystal molecules have an alignment order but do not have a three-dimensional positional order.

The heating temperature is preferably 50 to 120 ℃ and more preferably 60 to 100 ℃.

(curing of liquid Crystal composition)

When the liquid crystal composition contains a polymerizable liquid crystal compound, the aligned polymerizable liquid crystal compound may be polymerized by curing the liquid crystal composition. Curing may be performed by light irradiation or heating, and preferably by light irradiation. Preferably, the light irradiation is performed by using ultraviolet rays. Preferably, the irradiation energy is 20mJ/cm²～50J/cm²More preferably 100mJ/cm²～1,500mJ/cm². In order to promote the photopolymerization reaction, the light irradiation may be performed under heating conditions or under a nitrogen atmosphere. The wavelength of the ultraviolet radiation is preferably 250nm to 430 nm. From the viewpoint of stability, the polymerization reaction rate is preferably high, and is preferably 70% or more, and more preferably 80% or more. The polymerization reaction rate can be determined by the consumption ratio of the polymerizable functional group using IR absorption spectroscopy.

< support body >

The substrate may include a support. Examples of the support include glass, cellulose Triacetate (TAC), polyethylene terephthalate (PET), polycarbonate, polyvinyl chloride, acrylic, and polyolefin.

< alignment layer >

The substrate may also comprise an alignment layer. The alignment layer may be located between the support and the liquid crystal layer in the substrate including the support. In this case, the alignment layer is preferably in direct contact with the liquid crystal layer and the support. The alignment layer can be formed by a method such as rubbing treatment of an organic compound such as a polymer (a resin such as polyimide, polyvinyl alcohol, polyester, polyarylate, polyamideimide, polyetherimide, polyamide, or modified polyamide), oblique vapor deposition of an inorganic compound, formation of a layer having microgrooves, or accumulation of an organic compound (for example, ω -tricosanoic acid, octacosylmethylammonium chloride, or methyl stearate) by Langmuir-Blodgett (LB film) method. An alignment layer that generates an alignment function by applying an electric field, a magnetic field, or light irradiation may also be used.

In particular, it is preferable that the alignment layer containing a polymer is rubbed and then the liquid crystal composition is applied to the rubbed surface. The rubbing treatment can be performed by rubbing the surface of the polymer layer several times in a certain direction with paper or cloth.

The liquid crystal layer may be formed on the surface of the support or on the surface of the support subjected to rubbing treatment without providing the alignment layer.

The thickness of the alignment layer is preferably 0.01 to 5 μm, and more preferably 0.05 to 2 μm.

< Point >

The optical member of the present invention includes dots formed on a surface of a substrate. The surface of the substrate on which the dots are formed may be both surfaces of the substrate or may be one surface, but is preferably one surface.

One or more dots may be formed on the surface of the substrate. The two or more dots may be formed in plural numbers so as to be close to each other on the substrate surface, and the total surface area of the dots may be 50% or more, 60% or more, 70% or more, or the like of the area of the dot formation side surface of the substrate. In this case, the optical characteristics such as selective reflectivity of the dots may be substantially the optical characteristics of the entire optical member, particularly the optical characteristics of the entire surface of the dot formation surface. On the other hand, a plurality of two or more dots may be formed on the substrate surface so as to be spaced apart from each other, and the total surface area of the dots may be 50%, 30%, 10%, or less, or the like, which is smaller than the area of the dot formation side surface of the substrate. As in this case, the optical characteristics of the dot formation surface side of the optical member may be characteristics that can be confirmed as a contrast between the optical characteristics of the substrate and the optical characteristics of the dots.

The plurality of dots may be formed in a pattern, having a function of presenting information. For example, by forming the optical member in a sheet shape so as to provide positional information, the optical member can be used as a sheet capable of inputting data by being attached to a display.

When the dots are formed in a pattern, and for example, when a plurality of dots having a diameter of 20 to 200 μm are formed, 10 to 100 dots may be included in each square of 2mm square on the substrate surface, preferably 15 to 50 dots, and more preferably 20 to 40 dots.

When the substrate surface has a plurality of dots, the dots may have the same diameter and shape, or may have different diameters and shapes. For example, dots having the same diameter and shape are intended to be formed, but dots formed under the same conditions are preferable.

In the present specification, when points are described, the description can be applied to all points in the optical member of the present invention, but the optical member of the present invention including the described points is assumed to be allowed to include points that are not equivalent to the same description due to errors, mistakes, and the like that are allowed in the present technical field.

[ shape of dot ]

The shape of the dot is not particularly limited, but is preferably circular when viewed from the substrate normal direction. The circular shape may be not a perfect circle, but a substantially circular or elliptical shape. For example, the shape may be a shape in which a plurality of circles are overlapped while being deviated little by little. In terms of points, the term center denotes the center or center of gravity of the circle. When a plurality of dots are present on the substrate surface, the shapes of the dots may be the same or different, but are preferably the same or at least similar.

The diameter of the dots is preferably 20 to 200 μm, more preferably 30 to 150 μm. When the point is not a circle, the diameter of the point is set to a value measured or calculated to approximate a circle.

The diameter of a dot can be obtained by measuring the length of a straight line that passes from an end (edge or boundary portion of the dot) to the end and passes through the center of the dot in an image obtained using a microscope such as a laser microscope, a Scanning Electron Microscope (SEM), or a Transmission Electron Microscope (TEM). The number of dots and the distance between dots can also be confirmed in a microscope image of a laser microscope, a Scanning Electron Microscope (SEM), a Transmission Electron Microscope (TEM), or the like.

Preferably, the dots include portions having heights that continuously increase to a maximum height in a direction from the ends of the dots toward the center. In this specification, the above-mentioned portion may be referred to as an inclined portion or a curved portion. That is, the dots preferably include an inclined portion, a curved portion, or the like, which increases in height from the end of the dot toward the center.

In addition, in the present specification, when a dot is referred to as "height", it means "the shortest distance from a point on the surface of the dot to the dot formation side surface of the substrate". When the substrate has irregularities, the extending portion of the substrate surface at the end of the dot is defined as the dot-forming-side surface. The maximum height is the maximum value of the above-mentioned heights, and is, for example, the shortest distance from the apex of the point to the point-forming side surface of the substrate. The height of the spot can be confirmed from a cross-sectional view of the spot scanned at the focal position by a laser microscope or obtained by a microscope such as SEM or TEM.

Examples of the structure including the inclined portion or the curved portion include a hemispherical shape in which the substrate side is a plane, a shape (spherical trapezoidal shape) in which an upper portion of the hemispherical shape is cut substantially parallel to the substrate and flattened, a conical shape in which the substrate side is a bottom surface, a shape (conical trapezoidal shape) in which an upper portion of the conical shape is cut substantially parallel to the substrate and flattened, and a shape that can be approximated to any of these. Among these, a hemispherical shape in which the substrate side is a plane, a shape in which the upper portion of the hemispherical shape is cut substantially parallel to the substrate and flattened, a shape in which the conical upper portion in which the substrate side is a bottom surface is cut substantially parallel to the substrate and flattened, and a shape that can be approximated to any of these are preferable. The hemispherical shape includes not only a hemispherical shape in which a plane including the center of the ball is a plane but also any segment shape obtained by cutting the ball into two arbitrary pieces.

The point of the point surface providing the maximum height of the point may be the apex of the hemispherical or conical shape or a surface which is cut substantially parallel to the substrate and flattened as described above. It is also preferable that all the flat dots to be flattened provide the maximum height of the dots. It is also preferred that the center of the dot provide the maximum height.

In this regard, the value obtained by dividing the maximum height by the diameter of the dot (maximum height/diameter) is preferably 0.13 to 0.30. In particular, it is preferable that the above-mentioned contents are satisfied in a shape in which the substrate side is a flat hemispherical shape, an upper portion of the hemispherical shape is cut substantially parallel to the substrate and flattened, a conical upper portion having the substrate side as a bottom surface is cut substantially parallel to the substrate and flattened, and the like, and the height of the dots is continuously increased from the end portions of the dots to the maximum height, and the center indicates the maximum height. More preferably, the maximum height/diameter is 0.16 to 0.28.

An angle (for example, an average value) formed between the surface of the dot and the substrate (the dot formation side surface of the substrate) is preferably 27 degrees to 62 degrees, and more preferably 29 degrees to 60 degrees. Due to such an angle, it is possible to provide a dot exhibiting high retroreflectivity at an incident angle of light suitable for the application of an optical member to be described later.

The angle can be confirmed from a cross-sectional view of a point obtained by scanning a focal position of a laser microscope or using a microscope such as SEM or TEM, but in the present specification, the angle is determined by measuring an angle of a contact portion between a substrate and a surface of the point in an SEM image of a cross-sectional view including a center of the point on a plane perpendicular to the substrate.

[ optical Properties of spots ]

The dots in the optical member of the present invention exhibit wavelength selective reflectivity.

The light having dot display selective reflectivity is not particularly limited, and may be any of infrared light, visible light, ultraviolet light, and the like

For example, when the optical member is attached to a display and used as an optical member for inputting data by directly writing a hand on the display device, the wavelength of the light having selective reflectivity for dot display is preferably a wavelength in the invisible light region, more preferably a wavelength in the infrared light region, and particularly preferably a wavelength in the near-infrared light region so as not to affect the display image. For example, it is preferable that the reflection spectrum of the spot has a reflection wavelength band having a center wavelength in a range of 750 to 2000nm (preferably in a range of 800 to 1500 nm). The reflection wavelength is also preferably selected in accordance with the wavelength of light irradiated from a light source used in combination or the wavelength of light detected by an imaging element (sensor).

Further, for example, when the optical member of the present invention is used as a transparent screen, it is preferable that the light having selective reflectivity is displayed in a dot pattern in a visible light region. The reflection wavelength is preferably selected in accordance with light irradiated from an imaging device used in combination.

Preferably the dots are transparent in the visible region. Also, the dots may be colored, but preferably are not colored or are colored by a small amount. All of them are intended to prevent degradation of visibility of an image displayed on a display when an optical member is used in front of the display, for example. And, for preferred use as a transparent screen.

[ cholesteric Structure ]

The dots comprise a liquid crystal material having a cholesteric structure.

Cholesteric structures are known to exhibit selective reflectivity at specific wavelengths. The central wavelength (reflection peak wavelength) λ of the selective reflection depends on the pitch P of the helical structure in the cholesteric structure (i.e., the period of the helix), and satisfies the relationship of λ n × P with the average refractive index n of the cholesteric liquid crystal. Therefore, by adjusting the pitch of the helical structure, the selective reflection wavelength can be adjusted. The pitch of the cholesteric structure depends on the kind of the chiral agent used together with the liquid crystal compound at the time of forming the dot or the concentration of the chiral agent added, and thus a desired pitch can be obtained by adjusting the kind of the chiral agent.

The selectively reflected light of the cholesteric structure is circularly polarized light selective, and the selectively reflected light of the cholesteric structure is right circularly polarized light or left circularly polarized light. Whether the reflected light is right circularly polarized light or left circularly polarized light depends on the twist direction of the helix of the cholesteric structure. The cholesteric structure reflects right circularly polarized light when the twist direction of the helix is right, and reflects left circularly polarized light when the twist direction of the helix is left.

The adjustment of the pitch is described in detail in Fuji film (FUJIFILM) research report No.50 (2005) p.60-63. As the method for measuring the twist direction and pitch of the helix, a method described in "liquid crystal chemistry experimental entry" japan liquid crystal society, SIGMA (SIGMA) publication, 2007 publication, page 46, and "liquid crystal accessibility editorial committee pill 196 can be used.

The cholesteric structure was observed using a Scanning Electron Microscope (SEM) as a fringe pattern of the bright and dark portions. The repetition of the light and dark portions 2 times (two light and two dark portions) corresponds to 1 pitch part of the spiral. Therefore, the pitch can be measured from the SEM cross-sectional view. The normal line of each line of the stripe pattern is the spiral axis direction.

In the half width Δ λ (nm) of the selective reflection band (circularly polarized light reflection band) showing selective reflection, Δ λ depends on the birefringence Δ n of the liquid crystal compound and the above-mentioned pitch P, and satisfies a relationship of Δ λ ═ Δ n × P. Therefore, the control of selecting the width of the reflection band can be performed by adjusting Δ n. The Δ n can be adjusted by adjusting the kind and the mixing ratio of the polymerizable liquid crystal compound, or by controlling the temperature at which the alignment is fixed. The half width of the reflection wavelength band may be adjusted depending on the use of the optical member of the present invention, and is, for example, 50 to 500nm, preferably 100 to 300 nm.

[ cholesteric structure in dot ]

Within the dot, the helical axis of the cholesteric structure is preferably in an angular range of 50 to 90 degrees from the surface of the dot. The angle is more preferably 60 degrees to 90 degrees, and still more preferably 70 degrees to 90 degrees. In particular, at the surface of the dot, the angle formed by the helical axis of the cholesteric structure and the surface is preferably in the range of 70 to 90 degrees.

When a cross section of a point is observed using a Scanning Electron Microscope (SEM), the helical axis of the cholesteric structure is located in the normal direction of the line formed by each dark portion. At the surface of the dot, the angle formed by the helical axis of the cholesteric structure and the surface is the angle formed by the normal of the line formed from the 1 st dark part from the surface of the dot and the surface. When the surface is a curved line, the angle may be determined by taking the surface as a tangent to the surface in the cross section. In particular, in the inclined portion or the curved portion, by satisfying the angle, it is possible to exhibit high retroreflectivity even with respect to light incident on a point in a direction forming an angle from a normal direction of the substrate. For example, the optical member of the present invention can exhibit high retroreflectivity even in a form without a topcoat against light incident on a spot at a polar angle of 5 degrees or light incident on a spot at a polar angle of 30 degrees.

In particular, the angle formed by the helical axis of the cholesteric structure and the surface at a part of the inclined portion or the curved portion satisfies 70 to 90 degrees, and for example, the angle is preferably satisfied continuously but not intermittently at a part of the inclined portion or the curved portion. The angle is an acute angle, and for example, when the angle is in a range of 70 to 90 degrees, the angle formed by the normal line and the surface is in a range of 70 to 110 degrees when the angle is in a range of 0 to 180 degrees. In the cross-sectional view, the angle formed by the normal line of the line formed from the surface of the point to the 2 nd dark part is preferably in the range of 70 to 90 degrees, more preferably the angle formed by the normal line of the line formed from the surface of the point to the 3 rd to 4 th dark parts is in the range of 70 to 90 degrees, and still more preferably the angle formed by the normal line of the line formed from the 5 th to 12 th dark parts is in the range of 70 to 90 degrees.

At the surface of the dot, the angle formed by the helical axis of the cholesteric structure and the surface is more preferably in the range of 0 to 90 degrees, and still more preferably in the range of 85 to 90 degrees.

Cholesteric structures can be obtained by fixing the cholesteric liquid crystal phase. The structure in which the cholesteric liquid crystal phase is fixed may be a structure in which the alignment of the liquid crystal compound that has become the cholesteric liquid crystal phase is maintained, and typically, the structure may be a structure in which a polymerizable liquid crystal compound is brought into an aligned state of the cholesteric liquid crystal phase, and then polymerized and cured by ultraviolet irradiation, heating, or the like to form a layer having no fluidity, and at the same time, the layer is changed into a state in which the alignment form is not changed by an external field or an external force. In the structure in which the cholesteric liquid crystal phase is fixed, the optical properties of the cholesteric liquid crystal phase can be sufficiently maintained, and the liquid crystal compound may not exhibit liquid crystallinity. For example, a polymerizable liquid crystal compound can be converted to a high molecular weight by a curing reaction and loses liquid crystallinity.

[ method of Forming dots ]

For example, dots can be formed by applying a liquid crystal composition described later to the surface of the liquid crystal layer of the substrate, drying the composition, and curing the composition as needed. The liquid crystal layer may be surface processed before dot formation. For example, hydrophilic treatment or formation of a concave-convex shape may be performed to form dots having a desired shape or a desired dot pattern.

(discharge of liquid Crystal composition)

The application of the liquid crystal composition to the substrate for dot formation is preferably performed by discharging droplets. When a plurality of dots are used on the substrate, the liquid crystal composition may be printed as ink. The printing method is not particularly limited, and an ink jet method, a gravure printing method, a flexographic printing method, and the like can be used. The dot pattern can be formed by applying a known printing technique.

(drying of liquid Crystal composition)

The liquid crystal composition used on the surface of the substrate may be dried as necessary. The liquid crystal composition may be dried or heated after drying, and the liquid crystal compound in the liquid crystal composition may be aligned to form a cholesteric liquid crystal phase in the drying or heating step. When heating is performed, the heating temperature is preferably 200 ℃ or lower, more preferably 130 ℃ or lower.

(curing of liquid Crystal composition)

< liquid crystal composition >

Hereinafter, a liquid crystal composition which is a material that can be used for forming a liquid crystal layer and forming dots (cholesteric structure) will be described.

The liquid crystal composition comprises a liquid crystal compound. The liquid crystal compound is preferably a polymerizable liquid crystal compound. The liquid crystal composition may further contain a surfactant, a polymerization initiator, or the like. Preferably, the liquid crystal composition used for dot formation comprises a chiral agent.

[ polymerizable liquid Crystal Compound ]

The polymerizable liquid crystal compound may be a rod-like liquid crystal compound or a discotic liquid crystal compound, but is preferably a rod-like liquid crystal compound.

Examples of the rod-like polymerizable liquid crystal compound forming the cholesteric liquid crystal layer include a rod-like nematic liquid crystal compound. As the nematic liquid crystal compound in rod form, azomethines, azoxides, cyanobiphenyls, cyanophenyl esters, benzoates, phenyl cyclohexanecarboxylates, cyanophenylcyclohexanes, cyano-substituted phenyl pyrimidines, alkoxy-substituted phenyl pyrimidines, phenyl dioxanes, tolans and alkenylcyclohexanebenznitriles are preferably used. Not only low molecular liquid crystal compounds but also high molecular liquid crystal compounds can be used.

The polymerizable liquid crystal compound can be obtained by introducing a polymerizable group into a liquid crystal compound. Examples of the polymerizable group include an unsaturated polymerizable group, an epoxy group, and an aziridine group, and an unsaturated polymerizable group is preferable, and an ethylenically unsaturated polymerizable group is particularly preferable. The polymerizable group can be introduced into the molecule of the liquid crystal compound by various methods. The number of the polymerizable groups of the polymerizable liquid crystal compound is preferably 1 to 6, and more preferably 1 to 3. Examples of the polymerizable liquid crystal compound include compounds described in Makromol. chem.,190, 2255 (1989), Advanced Materials 5, 107 (1993), U.S. Pat. No. 4683327, U.S. Pat. No. 5622648, U.S. Pat. No. 5770107, International publication No. WO95/22586, International publication No. WO95/24455, International publication No. WO97/00600, International publication No. WO98/23580, International publication No. WO98/52905, Japanese patent application laid-open No. 1-272551, Japanese patent application laid-open No. 6-16616, Japanese patent application laid-open No. 7-110469, Japanese patent application laid-open No. 11-80081, Japanese patent application laid-open No. 2001-328973, Japanese patent application laid-open No. 2014-198815, and Japanese patent application laid-open publication No. 2014-198814. Two or more polymerizable liquid crystal compounds may be used in combination. When two or more polymerizable liquid crystal compounds are used in combination, the alignment temperature can be lowered.

Specific examples of the polymerizable liquid crystal compound include compounds represented by the following formulas (1) to (11).

[ chemical formula 1]

[ chemical formula 2]

(Compound (11) wherein X¹Is an integer of 2 to 5. )

As other polymerizable liquid crystal compounds than those mentioned above, cyclic organosiloxane compounds having a cholesteric phase as disclosed in JP-A-57-165480 can be used. Further, as the polymer liquid crystal compound, a polymer in which mesogenic groups for expressing liquid crystals are introduced into the main chain, the side chain, or both the main chain and the side chain, a polymer cholesteric liquid crystal in which a cholesteric group is introduced into the side chain, a liquid crystal polymer as disclosed in Japanese patent laid-open No. 9-133810, a liquid crystal polymer as disclosed in Japanese patent laid-open No. 11-293252, or the like can be used.

The amount of the polymerizable liquid crystal compound added to the liquid crystal composition is preferably 75 to 99.9% by mass, more preferably 80 to 99% by mass, and particularly preferably 85 to 90% by mass, based on the mass of the solid content (mass after removal of the solvent) of the liquid crystal composition.

[ chiral reagent (optically active Compound) ]

Preferably, the liquid crystal composition used for dot formation comprises a chiral agent. The chiral agent has a function of inducing a helical structure of a cholesteric liquid crystal phase. Since the direction of twist or the pitch of the helix induced by the compound is different, the chiral compound may be selected according to the purpose.

The chiral reagent is not particularly limited, and known compounds (for example, in chapter 3, 4-3 of the handbook of liquid crystal devices, published by the Chiral reagent 199 for TN and STN, published by the Japan Society for the development of Science 142, published by the Committee 1989), isosorbide and isomannide derivatives can be used.

Axial chiral (axialchirality) compounds or planar chiral (planar chirality) compounds, which generally contain asymmetric carbon atoms but do not contain asymmetric carbon atoms, can also be used as chiral agents. Examples of the axial chiral compound or the planar chiral compound include binaphthyl, spiroalkene, p-cycloaralkyl, and derivatives thereof. The chiral agent may have a polymerizable group. When both the chiral agent and the liquid crystal compound have a polymerizable group, a polymer having a repeating unit derived from the polymerizable liquid crystal compound and a repeating unit derived from the chiral agent can be formed by a polymerization reaction of the polymerizable chiral agent and the polymerizable liquid crystal compound. In this embodiment, the polymerizable group of the polymerizable chiral agent is preferably the same as the polymerizable group of the polymerizable liquid crystal compound. Therefore, the polymerizable group of the chiral agent is also preferably an unsaturated polymerizable group, an epoxy group or an aziridine group, more preferably an unsaturated polymerizable group, and particularly preferably an ethylenically unsaturated polymerizable group.

Also, the chiral agent may be a liquid crystal compound.

Specific examples of the chiral reagent include compounds represented by the following formula (12).

[ chemical formula 3]

Wherein X is an integer of 2 to 5.

The content of the chiral agent in the liquid crystal composition is preferably 0.01 to 200 mol%, more preferably 1 to 30 mol%, based on the amount of the polymerizable liquid crystalline compound.

[ surfactant ]

Preferably, the liquid crystal composition comprises a surfactant. Examples of the surfactant include silicone surfactants and fluorine surfactants, and fluorine surfactants are preferable.

Specific examples of the surfactant include compounds described in [0082] to [0090] of Japanese patent laid-open No. 2014-119605, compounds described in [0031] to [ 0034 ] of Japanese patent laid-open No. 2012-203237, compounds exemplified in [0092] and [0093] of Japanese patent laid-open No. 2005-99248, compounds exemplified in [0076] to [0078] and [0082] to [0085] of Japanese patent laid-open No. 2002-129162, and fluoro (meth) acrylate polymers described in [ 0018 ] to [ 0043 ] of Japanese patent laid-open No. 2007-open No. 272185.

One kind of surfactant may be used alone, or two or more kinds may be used in combination.

As the fluorine-based surfactant, compounds represented by the general formula (I) described in Japanese patent laid-open Nos. 2014-119605 and [0082] to [0090] are particularly preferable.

[ chemical formula 4]

General formula (I)

(Hb¹¹-Sp¹¹-L¹¹-Sp¹²-L¹²)_m11-A¹¹-L¹³-T¹¹-L¹⁴-A¹²-(L¹⁵-Sp¹³-L¹⁶-Sp¹⁴-Hb¹¹)_n11

In the general formula (I), L¹¹、L¹²、L¹³、L¹⁴、L¹⁵、L¹⁶Each independently represents a single bond, -O-, -S-, -CO-, -COO-, -OCO-, -COS-, -SCO-, -NRCO-, -CONR- (wherein R in the general formula (I) represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms), -NRCO-, -CONR-has a solubility-reducing effect, and is more preferably-O-, -S-, -CO-, -COO-, -OCO-, -COS-, -SCO-from the viewpoint of stability of the compound, and is more preferably-O-, -CO-, -COO-, -OCO-. The alkyl group for R may be linear or branched. More preferably 1 to 3 carbon atoms, and examples thereof include methyl, ethyl and n-propyl.

Sp¹¹、Sp¹²、Sp¹³、Sp¹⁴Each independently represents a single bond or an alkylene group having 1 to 10 carbon atoms, more preferably a single bond or an alkylene group having 1 to 7 carbon atoms, and still more preferably a single bond or an alkylene group having 1 to 4 carbon atoms. Wherein the hydrogen atom of the alkylene group may be substituted with a fluorine atom. The alkylene group may be branched or unbranched, but is preferably an unbranched alkylene group. From the viewpoint of synthesis, Sp is preferred¹¹And Sp¹⁴Are identical, and Sp¹²And Sp¹³The same is true.

A¹¹、A¹²Is a 1-4 valent aromatic hydrocarbon group. The number of carbon atoms of the aromatic hydrocarbon group is preferably 6 to 22, more preferably 6 to 14, still more preferably 6 to 10, and still more preferably 6. A. the¹¹、A¹²The aromatic hydrocarbon group may have substitutionAnd (4) a base. Examples of such a substituent include an alkyl group having 1 to 8 carbon atoms, an alkoxy group, a halogen atom, a cyano group, and an ester group. For the description and preferred ranges of these groups, the following corresponding descriptions of T can be referred to. As opposed to A¹¹、A¹²Examples of the substituent of the aromatic hydrocarbon group include a methyl group, an ethyl group, a methoxy group, an ethoxy group, a bromine atom, a chlorine atom, and a cyano group. Molecules having more perfluoroalkyl moieties within the molecule can orient the liquid crystal with a smaller amount of addition, resulting in a reduction in haze, and therefore A is preferred¹¹、A¹²Has a valence of 4 so that more perfluoroalkyl groups are present in the molecule. From the viewpoint of synthesis, A is preferred¹¹And A¹²The same is true.

T¹¹Preferred expression(s)

[ chemical formula 5]

A divalent group or a divalent aromatic heterocyclic group (T described above)¹¹Wherein X in the above-mentioned group represents an alkyl group having 1 to 8 carbon atoms, an alkoxy group, a halogen atom, a cyano group or an ester group, and Ya, Yb, Yc and Yd each independently represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms), more preferably

[ chemical formula 6]

Further preferred is

[ chemical formula 7]

T above¹¹The number of carbon atoms of the alkyl group of X contained in (1) is 1 to 8, preferably 1 to 5, and more preferably 1 to 3. The alkyl group may be linear, branched or cyclic, and is preferably linear or branched. Examples of the preferable alkyl group include a methyl group, an ethyl group, and an n-propyl groupAnd isopropyl group, among which methyl group is preferred. With respect to the above T¹¹In (b), the alkyl moiety of the alkoxy group of X contained in (b) can be referred to the above-mentioned T¹¹The description and preferred ranges of the alkyl groups of X contained in (a) are desirable. As the above-mentioned T¹¹Examples of the halogen atom of X contained in (1) include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom, and a chlorine atom and a bromine atom are preferable. As the above-mentioned T¹¹Examples of the preferable ester group of X in (1) include a group represented by R' COO-. Examples of R' include alkyl groups having 1 to 8 carbon atoms. With regard to the description and preferred ranges of the alkyl groups which R' may assume, reference can be made to the above-mentioned T¹¹The description and preferred ranges of the alkyl groups of X contained in (a) are desirable. Specific examples of the ester include CH₃COO-、C₂H₅COO-is provided. The alkyl group having 1 to 4 carbon atoms which is preferable for Ya, Yb, Yc and Yd may be straight or branched. Examples thereof include methyl, ethyl, n-propyl, and isopropyl.

The divalent aromatic heterocyclic group preferably has a 5-, 6-or 7-membered heterocyclic ring. Further preferred is a 5-or 6-membered ring, most preferred is a 6-membered ring. As the hetero atom constituting the heterocyclic ring, a nitrogen atom, an oxygen atom and a sulfur atom are preferable. The heterocyclic ring is preferably an aromatic heterocyclic ring. The aromatic heterocyclic ring is usually an unsaturated heterocyclic ring. Further preferred are unsaturated heterocycles having the most double bonds. Examples of the heterocyclic ring include furan ring, thiophene ring, pyrrole ring, pyrroline ring, pyrrolidine ring, oxazole ring, isoxazole ring, thiazole ring, isothiazole ring, imidazole ring, imidazoline ring, imidazolidine ring, pyrazole ring, pyrazoline ring, pyrazolidine ring, triazole ring, furazan (furazane) ring, tetrazole ring, pyran ring, thiopyran (thiin) ring, pyridine ring, piperidine ring, oxazine ring, morpholine ring, thiazine ring, pyridazine ring, pyrimidine ring, pyrazine ring, piperazine ring, and triazine ring. The divalent heterocyclic group may have a substituent. With regard to the description and preferred ranges of examples of such substituents, reference can be made to A as described above¹And A²The 1 to 4 valent aromatic hydrocarbon of the desirable substituents are described and shown.

Hb¹¹Represents a C2-30 perfluoroalkyl group, more preferably a C3-20 perfluoroalkyl group, furtherThe preferable step is perfluoroalkyl with 3-10 carbon atoms. The perfluoroalkyl group may be linear, branched, or cyclic, but is preferably linear or branched, and more preferably linear.

m11 and n11 independently represent 0 to 3, and m11+ n11 is not less than 1. In this case, the structures in parentheses where a plurality of structures are present may be the same or different from each other, but are preferably the same. M11 and n11 in the general formula (I) are A¹¹、A¹²The valence of (A) is determined, and the preferable range is also determined by A¹¹、A¹²The preferable range of the valence number of (a).

T¹¹O and p contained in (a) are each independently an integer of 0 or more, and when o and p are 2 or more, a plurality of xs may be the same or different from each other. T is¹¹O contained in (1) is preferably 1 or 2. T is¹¹P in (1) is preferably an integer of 1 to 4, more preferably 1 or 2.

The compound represented by the general formula (I) may have a symmetrical molecular structure or may have no symmetry. Here, symmetry means a structure corresponding to at least one of point symmetry, line symmetry, and rotational symmetry, and asymmetry means a structure not corresponding to any of point symmetry, line symmetry, and rotational symmetry.

The compound represented by the general formula (I) is the perfluoroalkyl group (Hb)¹¹) A linking group- (-Sp)¹¹-L¹¹-Sp¹²-L¹²)_m11-A¹¹-L¹³-and-L¹⁴-A¹²-(L¹⁵-Sp¹³-L¹⁶-Sp¹⁴-)_n11And preferably T having a valence of 2 excluding the volume effect. Two perfluoroalkyl groups (Hb) present in the molecule¹¹) Preferably, the linking groups- (-Sp) are identical to each other and are present in the molecule¹¹-L¹¹-Sp¹²-L¹²)_m11-A¹¹-L¹³-and-L¹⁴-A¹²-(L¹⁵-Sp¹³-L¹⁶-Sp¹⁴-)_n11-are also preferably identical to each other. Terminal Hb¹¹-Sp¹¹-L¹¹-Sp¹²-and-Sp¹³-L¹⁶-Sp¹⁴-Hb¹¹Preferably, the group is represented by any one of the following formulae.

(C_aF_2a+1)-(C_bH_2b)-

(C_aF_2a+1)-(C_bH_2b)-O-(C_rH_2r)-

(C_aF_2a+1)-(C_bH_2b)-COO-(C_rH_2r)-

(C_aF_2a+1)-(C_bH_2b)-OCO-(C_rH_2r)-

In the above formula, a is preferably 2 to 30, more preferably 3 to 20, and further preferably 3 to 10. b is preferably 0 to 20, more preferably 0 to 10, and further preferably 0 to 5. a + b is 3 to 30. r is preferably 1 to 10, more preferably 1 to 4.

And terminal Hb of the general formula (I)¹¹-Sp¹¹-L¹¹-Sp¹²-L¹²-and-L¹⁵-Sp¹³-L¹⁶-Sp¹⁴-Hb¹¹Preferably, the group is represented by any one of the following formulae.

(C_aF_2a+1)-(C_bH_2b)-O-

(C_aF_2a+1)-(C_bH_2b)-COO-

(C_aF_2a+1)-(C_bH_2b)-O-(C_rH_2r)-O-

(C_aF_2a+1)-(C_bH_2b)-COO-(C_rH_2r)-COO-

(C_aF_2a+1)-(C_bH_2b)-OCO-(C_rH_2r)-COO-

The definitions of a, b and r in the above formula are the same as those of the above formula.

In particular, it is preferable that the liquid crystal layer-forming surfactant be capable of horizontally aligning liquid crystals and providing a desired liquid repellency. The structure is not particularly limited as long as this condition is satisfied, and as the surfactant for forming a liquid crystal layer, for example, a low-molecular surfactant or a copolymer surfactant as exemplified below is preferably used.

The low-molecular-weight surfactant is a compound having at least 6 perfluoroalkyl groups (CaF2a +1) in the molecule. a is preferably 4 or more, and more preferably 6 or more. Specifically, the compounds described in Japanese patent application laid-open Nos. 2013-47204 and 2002-129162 can be preferably used.

The copolymer surfactant is a copolymer containing a monomer having a perfluoroalkyl group represented by the following structure, and is a copolymer in which the mass ratio of the monomer having the following structure to all monomers is 25% or more. The mass ratio of the monomers is preferably 30% or more, and more preferably 35% or more. In the formula, a is preferably 4 or more, and more preferably 6 or more. In the formula, a2 represents an integer of 1 to 3, and most preferably 2. R represents methyl or hydrogen, more preferably hydrogen.

[ chemical formula 8]

Specifically, the copolymers described in Japanese patent application laid-open No. 2008-257205 and Japanese patent application laid-open No. 2004-198511 can be preferably used.

The amount of the surfactant added to the liquid crystal composition is preferably 0.01 to 10% by mass, more preferably 0.01 to 5% by mass, and particularly preferably 0.02 to 1% by mass, based on the total mass of the polymerizable liquid crystal compound.

In particular, in order to impart liquid repellency, the surfactant is preferably added in an amount more than the minimum amount necessary for the horizontal alignment of the liquid crystal in the liquid crystal composition for forming the liquid crystal layer. Specifically, the content is preferably 0.2% by mass or more, more preferably 0.3% by mass or more, and particularly preferably 0.4% by mass or more, based on the total mass of the polymerizable liquid crystal compound.

[ polymerization initiator ]

When the liquid crystal composition contains a polymerizable compound, it preferably contains a polymerization initiator. In the method of carrying out the polymerization reaction by ultraviolet irradiation, the polymerization initiator to be used is preferably a photopolymerization initiator which can start the polymerization reaction by ultraviolet irradiation. Examples of the photopolymerization initiator include an α -carbonyl compound (described in each specification of U.S. Pat. No. 2367661 and U.S. Pat. No. 2367670), an acyloin ether (described in each specification of U.S. Pat. No. 2448828), an α -hydrocarbon-substituted aromatic acyloin compound (described in each specification of U.S. Pat. No. 2722512), a polyquinone compound (described in each specification of U.S. Pat. No. 3046127 and U.S. Pat. No. 2951758), a combination of a triarylimidazole dimer and p-aminophenyl ketone (described in each specification of U.S. Pat. No. 3549367), an acridine and phenazine compound (described in Japanese patent laid-open publication No. Sho 60-105667 and U.S. Pat. No. 4239850), and an oxadiazole compound (described in U.S. Pat. No. 4212970).

The content of the photopolymerization initiator in the liquid crystal composition is preferably 0.1 to 20% by mass, and more preferably 0.5 to 12% by mass, based on the content of the polymerizable liquid crystal compound.

[ crosslinking agent ]

The liquid crystal composition may optionally contain a crosslinking agent for the purpose of improving the film strength after curing and improving the durability. As the crosslinking agent, a crosslinking agent that cures with ultraviolet rays, heat, moisture, or the like can be preferably used.

The crosslinking agent is not particularly limited and may be appropriately selected according to the purpose, and examples thereof include polyfunctional acrylate compounds such as trimethylolpropane tri (meth) acrylate and pentaerythritol tri (meth) acrylate; epoxy compounds such as glycidyl (meth) acrylate and ethylene glycol diglycidyl ether; aziridine compounds such as 2, 2-bis (hydroxymethyl) butanol-tris [3- (1-aziridinyl) propionate ], 4-bis (ethyleneiminocarbonylamino) diphenylmethane and the like; isocyanate compounds such as hexamethylene diisocyanate and biuret type isocyanate; a polyoxazoline compound having an oxazoline group in a side chain; and alkoxysilane compounds such as vinyltrimethoxysilane and N- (2-aminoethyl) 3-aminopropyltrimethoxysilane. In addition, a known catalyst can be used according to the reactivity of the crosslinking agent, and productivity can be improved in addition to the improvement of the membrane strength and durability. These may be used alone or in combination of two or more.

The content of the crosslinking agent is preferably 3 to 20% by mass, more preferably 5 to 15% by mass. If the content of the crosslinking agent is less than 3% by mass, the effect of increasing the crosslinking density may not be obtained, and if it exceeds 20% by mass, the stability of the cholesteric liquid crystal layer may be lowered.

[ other additives ]

The liquid crystal composition may comprise a monofunctional polymerizable monomer. In particular, it is preferable that the liquid crystal composition used for dot formation contains a monofunctional polymerizable monomer. This is because, when the ink jet method described later is used as the dot forming method, the ink properties usually obtained can be obtained by using the monofunctional polymerizable monomer. Examples of the monofunctional polymerizable monomer include 2-methoxyethyl acrylate, isobutyl acrylate, isooctyl acrylate, isodecyl acrylate, octyl acrylate/decyl acrylate, and the like.

If necessary, a polymerization inhibitor, an antioxidant, an ultraviolet absorber, a light stabilizer, a colorant, metal oxide fine particles, and the like may be added to the liquid crystal composition within a range not to deteriorate optical performance and the like.

[ solvent ]

The liquid crystal composition may contain a solvent. The solvent is not particularly limited and may be appropriately selected depending on the purpose, but an organic solvent is preferably used.

The organic solvent is not particularly limited and may be appropriately selected according to the purpose, and examples thereof include ketones such as methyl ethyl ketone and methyl isobutyl ketone, alkyl halides, amides, sulfoxides, heterocyclic compounds, hydrocarbons, esters, and ethers. These may be used alone or in combination of two or more. Among these, ketones are particularly preferable in view of environmental load. The above-mentioned components such as the above-mentioned monofunctional polymerizable monomer can function as a solvent.

< overcoat layer >

The optical component may also include an overcoat. The overcoat layer may be provided on the liquid crystal layer surface side of the substrate on which the dots are formed, and preferably, the surface of the optical member is planarized.

The overcoat layer is not particularly limited, but is preferably a resin layer having a refractive index of about 1.4 to 1.8. In order to prevent scattering of image light from an image display device when the optical member is used as an input medium such as an input sheet on a display surface of the image display device or the like, a difference in refractive index between the overcoat layer and the dots containing the liquid crystal material is preferably 0.2 or less. More preferably 0.1 or less. The refractive index of the dots containing the liquid crystal material is about 1.6, and the polar angle of light actually incident on the dots can be reduced by using the overcoat layer having a refractive index of about 1.4 to 1.8. For example, when light is incident on the optical member at a polar angle of 45 degrees using an overcoat layer having a refractive index of 1.6, the polar angle actually incident on the point can be about 27 degrees. Therefore, by using the overcoat layer, the polar angle of light exhibiting retroreflectivity of the optical member can be increased, and even in a point where the angle formed between the surface of the point and the substrate is small, high retroreflectivity can be obtained in a wider range. The overcoat layer may also function as an antireflection layer, an adhesive layer, or a hard coat layer.

Examples of the overcoat layer include a resin layer obtained by applying a composition containing a monomer to the liquid crystal layer surface side of the substrate on which the dots are formed, and then curing the coating film. The resin is not particularly limited, and may be selected in consideration of adhesion to a substrate or a liquid crystal material forming the dots, and the like. For example, a thermoplastic resin, a thermosetting resin, an ultraviolet curable resin, or the like can be used. From the viewpoint of durability, solvent resistance, and the like, a resin of a type that cures by crosslinking is preferable, and particularly, an ultraviolet-curable resin that can cure in a short time is preferable. Examples of monomers that can be used for forming the overcoat layer include ethyl (meth) acrylate, ethylhexyl (meth) acrylate, styrene, methylstyrene, N-vinylpyrrolidone, polyhydroxymethylpropane tri (meth) acrylate, hexanediol (meth) acrylate, tripropylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, 1, 6-hexanediol di (meth) acrylate, and neopentyl glycol di (meth) acrylate.

The thickness of the overcoat layer is not particularly limited, and may be determined in consideration of the maximum height of the dots, and may be about 5 μm to 100 μm, preferably 10 μm to 50 μm, and more preferably 20 μm to 40 μm. The thickness is the distance from the dot formation surface of the substrate at the non-dot portion to the overcoat surface on the opposite side.

< use of optical component >

The application of the optical member of the present invention is not particularly limited, and the optical member can be used as various reflective members.

For example, an optical member having a plurality of dots formed on the surface of the substrate in close proximity to each other can be used as a counter reflector for reflecting only circularly polarized light of a specific wavelength.

The optical member of the present invention can be used as a transparent screen. The wavelength range of selective reflection displayed by the dots is adjusted in accordance with the wavelength of the image light emitted from an imaging device such as a projector, whereby the image light can be reflected. In the optical member of the present invention, since only light in a specific wavelength region is reflected at a point, light is transmitted at a portion other than the point, and light other than the specific wavelength region is also transmitted at the point. Therefore, it is possible to provide a transparent screen that can be observed by superimposing the image light and the background on the back surface side.

The optical member having dots in a pattern is formed, for example, by using a pattern as a dot pattern which is coded to provide position information, and can be used as an input medium used in combination with an input means such as an electronic pen for digitizing handwritten information and inputting the digitized handwritten information to an information processing apparatus. In use, a liquid crystal material for forming dots is prepared and used so that the wavelength of light irradiated from the input means is a wavelength reflected by dot display. Specifically, the helical pitch of the cholesteric structure may be adjusted by the above-described method.

The optical member of the present invention can also be used as an input medium such as an input sheet on the surface of a display such as a liquid crystal display. At this time, the optical member is preferably transparent. The optical member may be bonded to the display surface directly or via another film or the like, and may be integrated with the display, or may be detachably attached to the display surface, for example. In this case, it is preferable that the wavelength region of the light selectively reflected by the dot display in the optical member of the present invention is different from the wavelength region of the light emitted from the display. That is, it is preferable that the display has selective reflectivity in the invisible light region and does not emit invisible light, so that erroneous detection by the detection device is avoided.

As a handwriting input system for digitizing handwritten information and inputting the digitized handwritten information into an information processing apparatus, reference can be made to japanese patent application laid-open nos. 2014-67398, 2014-98943, 2008-165385, 2008-108236 [0021] - [0032], 2008-077451, and the like.

Preferred embodiments of the optical member of the present invention used as a sheet attached to the front surface or the front side of a display device capable of displaying an image include those described in [0024] to [0031] of japanese patent No. 4725417.

Fig. 2 is a schematic diagram showing a system in which the optical member of the present invention is used as a sheet attached to the front surface or the front side of a display device capable of displaying an image.

In fig. 2, as long as the reflected light r of the pattern can be detected by emitting infrared rays i, there is no particular limitation, and a known sensor may be used, and examples of the pen-type input terminal 106 further including the read data processing device 107 include a pen tip which does not include ink, graphite, or the like, a CMOS (Complementary metal-Oxide Semiconductor) camera which includes an infrared ray irradiation portion, a processor, a memory, a communication interface such as a wireless transceiver using bluetooth (registered trademark) technology or the like, and a pen-type input terminal such as a battery, which are disclosed in japanese patent application laid-open No. 2003-256137.

As an operation of the pen-type input terminal 106, for example, when a pen tip is brought into contact with and drawn on the front surface of the optical component 100 of the present invention, the pen-type input terminal 106 detects a pen pressure in addition to the pen tip, the CMOS camera is activated, a predetermined range in the vicinity of the pen tip is irradiated with infrared rays of a predetermined wavelength emitted from the infrared ray irradiation unit, and a pattern is photographed (the pattern is photographed, for example, several tens to 100 times within 1 second). When the pen-type input terminal 106 includes the read data processing device 107, the captured pattern is analyzed by the processor, and the input trajectory accompanying the movement of the pen tip during handwriting is digitized and digitized to generate input trajectory data, and the input trajectory data is transmitted to the information processing device.

As shown in fig. 2, the read data processing device 107 may include a processor, a memory, a communication interface such as a wireless transceiver using Bluetooth (registered trademark) technology or the like, and a battery or the like, outside the pen input terminal 106. In this case, the pen-type input terminal 106 may be connected to the read data processing device 107 via a wire 108, or may wirelessly transmit read data using radio waves, infrared rays, or the like.

The input terminal 106 may be a reader as described in japanese patent application laid-open No. 2001-243006.

The read data processing device 107 that can be used in the present invention is not particularly limited as long as it has the following functions, and may include components such as a processor, a memory, a communication interface, and a battery. The function is to calculate position information from continuous imaging data read by the input terminal 106, and to combine the position information with time information to provide input trajectory data that can be processed by the information processing apparatus.

The read data processing device 107 may be incorporated in the input terminal 106 as described in japanese patent application laid-open No. 2003-256137, or may be incorporated in an information processing device provided with a display device. The read data processing device 107 may wirelessly transmit the position information to an information processing device provided with a display device, or may transmit the position information by a wired connection connected by a wire or the like.

The information processing device connected to the display device 105 can display the trajectory handwritten by the input terminal 106 on the display device as if writing with a pen on paper by sequentially updating the image displayed on the display device 105 based on the trajectory information transmitted from the read data processing device 107.

< image display device >

The image display device of the present invention has the optical member of the present invention.

For example, an image display device in which the optical member of the present invention is mounted on the front side of the image display surface of the image display device, such as the optical member of the present invention, is disposed on the frontmost surface of the display device or between the protective front panel and the display panel. A preferred embodiment of the image display device is described in the item of the application of the optical member.

Further, a system including an image display device in which the optical member of the present invention is mounted on an image display surface of the image display device or on the front side of the image display surface is also included in the invention disclosed in the present specification.

Examples

The present invention will be further specifically described below with reference to examples. The materials, reagents, amounts of substances, ratios thereof, operations and the like shown in the following examples can be appropriately modified without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the following examples.

[ example 1]

(preparation of liquid Crystal layer)

A liquid crystal layer-producing solution was prepared by stirring and dissolving a composition shown below in a container kept at 25 ℃.

[ chemical formula 9]

Rod-like liquid crystal compound

The numerical value is mass%. The group represented by R has a partial structure shown on the lower right side, and is bonded to the oxygen atom of the partial structure.

Surfactant A

In the formula, a represents 36.5 and b represents 63.5, and the polymer is randomly copolymerized at the mass ratio.

Subsequently, a polyimide alignment film SE-130 manufactured by Nissan Chemical Industries, ltd. was applied to the surface of the cleaned glass substrate by spin coating, dried, and then calcined at 250 ℃ for 1 hour. This was subjected to rubbing treatment to prepare a support with an alignment film. The liquid crystal layer-forming solution prepared above was applied to the rubbing surface of the alignment film by spin coating at 2000 rpm, subjected to alignment aging at 80 ℃ for 30 seconds, and then irradiated at 30 ℃ with a high-pressure mercury lamp that blocks the short-wavelength component of ultraviolet rays at 500mJ/cm²The alignment state is fixed by the ultraviolet rays of (1), thereby obtaining a liquid crystal layer.

(formation of cholesteric liquid Crystal dot)

Cholesteric liquid crystal ink (liquid crystal composition) was prepared by stirring and dissolving the following composition in a container kept at 25 ℃.

[ chemical formula 10]

Rod-like liquid crystal compound

[ chemical formula 11]

Chiral reagents

Surface active agent

On the liquid crystal layer on the glass substrate prepared as described above, droplets of the cholesteric liquid crystal ink prepared as described above were discharged over the entire area of 50 × 50mm with a distance between dot centers of 75 μm by an ink jet printer (DMP-2831, manufactured by FUJIFILLMDimatix Co., Ltd.), dried at 95 ℃ for 30 seconds, and then irradiated with 500mJ/cm by an ultraviolet irradiation apparatus²Thereby obtaining an optical member.

(evaluation of dot shape and cholesteric texture)

When 10 dots of the optical member obtained as described above were randomly selected and the shape of the dots was observed using a laser microscope (manufactured by keyence electron corporation), the average diameter of the dots was 22 μm, the average maximum height was 6.2 μm, and the height was continuously increased in the direction from the end to the center of the dots.

(evaluation of Spot Performance)

The results of measuring 5 sites at random under a field of view having a diameter of 2mm using a visible-near infrared irradiation light source (HL-2000) manufactured by Ocean Optics, an ultra-high resolution fiber multichannel spectrometer (HR4000), and a 2-branch optical fiber, revealed that the reflection peak wavelength in any site was 560nm, and that retroreflection was always confirmed from all points when the normal line of the optical member was 0 degree and confirmed at polar angles of 5 degrees and 30 degrees. Fig. 3 shows a measurement image of the optical member at a polar angle of 5 degrees.

[ example 2]

An optical member was produced in the same manner as in example 1, except that the surfactant in the liquid crystal layer preparation solution of example 1 was changed to surfactant B having the following structure, and the addition amount was changed from 0.6 to 0.3.

[ chemical formula 12]

Surfactant B

[ example 3]

After rubbing 75 μm thick PET (polyethylene terephthalate, TOYOBO CO., LTD., manufactured), the liquid crystal layer-forming solution of example 1 was bar-coated to a wet film thickness of 4 μm, dried at 85 ℃ for 1 minute and cured, and then irradiated at 30 ℃ with 500mJ/cm using a high-pressure mercury lamp that blocks short-wavelength components of ultraviolet rays²The alignment state is fixed by the ultraviolet rays of (1), thereby obtaining a liquid crystal layer. The subsequent steps produce an optical member in the same manner as in example 1.

(evaluation of dot shape and cholesteric texture)

As in example 1, 10 dots of the optical member obtained as described above were randomly selected, and the shape of the dots was observed with a laser microscope (manufactured by KEYENCE CORPORATION), and as a result, the height was continuously increased in the direction from the end portions of the dots toward the center.

Then, one point located at the center of the optical member obtained as described above was cut perpendicularly to the PET substrate on a plane including the center of the point, and a cross section was observed using a scanning electron microscope. As a result, a stripe pattern of a light portion and a dark portion was observed in the dot, and a cross-sectional view as shown in fig. 4 was obtained.

From the cross-sectional view, it was confirmed that the angle formed between the normal line direction of the line formed by the 1 st dark portion from the surface on the air interface side of the dot and the surface on the air interface side was in the range of 70 degrees to 90 degrees with respect to the helical axis of the cholesteric structure (the normal line direction of the line formed by the dark portion).

[ example 4]

After a liquid crystal layer was formed in the method of example 3 using the liquid crystal layer coating liquid of example 2, an optical member was produced in the same manner as in example 1.

[ example 5]

(formation of alignment layer)

The coating liquid for an alignment layer was applied to TAC (cellulose triacetate, manufactured by fujifilm corporation) having a thickness of 80 μm, and the substrate with an alignment film was produced by drying the solvent at 100 ℃ for 2 minutes and then rubbing the dried solvent.

Next, a liquid crystal layer was formed by the method of example 3 using the liquid crystal layer-forming solution of example 1. The subsequent steps produce an optical member in the same manner as in example 1.

The dots of the optical member obtained had an average diameter of 26 μm and an average maximum height of 5.9 μm.

[ example 6]

A liquid crystal layer was formed on a TAC substrate in the same manner as in example 5 using the liquid crystal layer-making solution of example 2. The subsequent steps produce an optical member in the same manner as in example 1.

The dots of the obtained optical member had an average diameter of 35 μm and an average maximum height of 4.7 μm.

Comparative example 1

An optical member was produced in the same manner as in example 1, except that the substrate used in example 1 was changed to glass without an alignment film and no liquid crystal layer was formed.

Comparative example 2

An optical member was produced in the same manner as in example 1 except that the liquid crystal layer (only glass with an alignment film) was not formed on the substrate used in example 1.

Comparative example 3

An optical member was produced in the same manner as in example 3, except that the solution for producing a liquid crystal layer formed on the substrate used in example 3 was changed to the following composition and a non-liquid crystal layer was formed.

Comparative example 4

An optical member was produced in the same manner as in example 3 except that the liquid crystal layer was not formed on the base material used in example 3 (only rubbing-treated PET).

In the same manner as in example 1, in examples 2 to 4 and comparative examples 1 to 4, the dot diameter, the maximum height/diameter, and the presence or absence of retroreflection at a polar angle of 5 degrees or 30 degrees when the normal line of the optical member was 0 degree were measured and confirmed. The results are shown in Table 1.

[ Table 1]

Reflection A: retroreflection can be confirmed.

Reflection B: retroreflection cannot be confirmed or is very weak.

The dot-forming cholesteric liquid crystal layer of the sample of the example was aligned and retroreflection was confirmed at all angles.

In the sample of comparative example 1, the cholesteric alignment of the formed dots was disturbed, and the maximum height of the dots was low, so that retroreflection was not confirmed.

The cholesteric type of the formed dots of the samples of comparative examples 2 and 4 were aligned, but since the maximum height of the dots was low, the retroreflection at 5 degrees was very weak, and the retroreflection at 30 degrees could not be confirmed.

Since the cholesteric alignment of the formed dots of the sample of comparative example 3 was disturbed and the maximum dot height was sufficiently high, the retroreflection at 5 degrees was very weak, and 30 degrees was confirmed.

Example 7: optical Member with overcoat layer

A coating liquid for an overcoat layer was prepared by stirring and dissolving a composition shown below in a vessel kept at 25 ℃.

The liquid crystal layer having cholesteric liquid crystal dots formed thereon was coated with a bar coater at a rate of 40mL/m²The coating amount of (3) was determined by coating the coating liquid for overcoat layer prepared above. Then, the film was heated to 50 ℃ and dried for 60 seconds, and then irradiated with 500mJ/cm by an ultraviolet irradiation device²The ultraviolet ray of (2) causes a crosslinking reaction to proceed, thereby producing an overcoat layer.

The optical member having the obtained overcoat layer was subjected to point property evaluation.

As a result of randomly measuring 5 sites in a field of view having a diameter of 2mm using a visible-near infrared irradiation light source (HL-2000) manufactured by Ocean Optics, an ultra-high resolution fiber multichannel spectrometer (HR4000), and a 2-branch optical fiber, it was found that the reflection peak wavelength in any site of the field of view was 560nm, and when the normal line of the optical member was 0 degree and confirmed in the range of polar angles 5 degrees and 50 degrees, retroreflection was always confirmed from all points.

[ example 8]

An optical member was produced in the same manner as in example 1, except that the amount of the chiral agent added to the cholesteric liquid crystal ink in example 1 was changed from 5.5 parts by mass to 3.8 parts by mass.

The dots of the obtained optical member had an average diameter of 23 μm and an average maximum height of 6.0. mu.m.

Next, an overcoat layer was formed in the same manner as in example 7, and dot performance evaluation was performed in the same manner as in example 7. As a result, retroreflection was always observed from all points when observation was performed in a range of 0 to 50 degrees with the normal line of the optical member set to 0 degree and the reflection peak wavelength was 850nm in the field of view at any position.

Description of the symbols

1-dot, 2-substrate, 3-support, 4-liquid crystal layer, 5-overcoat, 100-optics, 105-display, 106-pen input, 107-read data processing, 108-wire.

Claims

1. An optical member having a substrate and a point in contact with a surface of the substrate,

the dots comprising a liquid crystal material having a cholesteric structure,

the substrate includes a liquid crystal layer on a surface in contact with the point,

the liquid crystal layer is a layer in which the horizontal orientation of a rod-like liquid crystal compound is fixed.

2. The optical component of claim 1,

the liquid crystal layer is a cured layer of a composition containing a polymerizable rod-like liquid crystal compound.

3. The optical component of claim 1,

the liquid crystal layer includes a surfactant.

4. The optical component of claim 1,

the substrate includes an alignment film, and the liquid crystal layer is in direct contact with the alignment film.

5. The optical component of claim 1,

the substrate includes a support.

6. The optical component of claim 1,

the liquid crystal material is obtained by curing a liquid crystal composition containing a liquid crystal compound and a chiral reagent.

7. The optical component of claim 6,

the liquid crystal composition includes a surfactant.

8. The optical component of claim 7,

the surfactant is a fluorine surfactant.

9. The optical component of claim 1,

the surface of the substrate has a plurality of dots in a pattern.

10. The optical component of claim 1,

the diameter of the dots is 20-200 μm.

11. The optical component of claim 1,

the maximum height of the dots divided by the diameter of the dots is 0.13 to 0.30.

12. The optical component of claim 1,

the dots have wavelength selective reflectivity with a center wavelength in the infrared light region.

13. The optical component of claim 12,

the dots have wavelength selective reflectivity having a center wavelength at a wavelength of 800 to 950 nm.

14. An optical component in accordance with any one of claims 1 to 13 wherein the optical component is transparent.

15. An image display device having the optical member according to claim 14.